/**
 * IK 中文分词  版本 5.0.1
 * IK Analyzer release 5.0.1
 * 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * 源代码由林良益(linliangyi2005@gmail.com)提供
 * 版权声明 2012，乌龙茶工作室
 * provided by Linliangyi and copyright 2012 by Oolong studio
 * 

 * 
 */
package org.wltea.analyzer.lucene;

import java.io.IOException;  
import java.io.Reader;  
  
import org.apache.lucene.analysis.Tokenizer;  
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;  
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;  
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;  
  
import org.wltea.analyzer.core.IKSegmenter;  
import org.wltea.analyzer.core.Lexeme;  
  
/** 
 * IK分词器 Lucene Tokenizer适配器类 兼容Lucene 6.5.0版本 暴走抹茶 2017.3.28 
 */  
public final class IKTokenizer extends Tokenizer {  
  
    // IK分词器实现  
    private IKSegmenter _IKImplement;  
  
    // 词元文本属性  
    private final CharTermAttribute termAtt;  
    // 词元位移属性  
    private final OffsetAttribute offsetAtt;  
    // 词元分类属性（该属性分类参考org.wltea.analyzer.core.Lexeme中的分类常量）  
    private final TypeAttribute typeAtt;  
    // 记录最后一个词元的结束位置  
    private int endPosition;  
  
    public IKTokenizer(Reader in) {  
        this(in, false);  
    }  
  
    /** 
     * Lucene 6.5.0 Tokenizer适配器类构造函数 
     *  
     * @param in 
     * @param useSmart 
     */  
    public IKTokenizer(Reader in, boolean useSmart) {  
        offsetAtt = addAttribute(OffsetAttribute.class);  
        termAtt = addAttribute(CharTermAttribute.class);  
        typeAtt = addAttribute(TypeAttribute.class);  
        _IKImplement = new IKSegmenter(input, useSmart);  
    }  
  
    /* 
     * (non-Javadoc) 
     *  
     * @see org.apache.lucene.analysis.TokenStream#incrementToken() 
     */  
    @Override  
    public boolean incrementToken() throws IOException {  
        // 清除所有的词元属性  
        clearAttributes();  
        Lexeme nextLexeme = _IKImplement.next();  
        if (nextLexeme != null) {  
            // 将Lexeme转成Attributes  
            // 设置词元文本  
            termAtt.append(nextLexeme.getLexemeText());  
            // 设置词元长度  
            termAtt.setLength(nextLexeme.getLength());  
            // 设置词元位移  
            offsetAtt.setOffset(nextLexeme.getBeginPosition(), nextLexeme.getEndPosition());  
            // 记录分词的最后位置  
            endPosition = nextLexeme.getEndPosition();  
            // 记录词元分类  
            typeAtt.setType(nextLexeme.getLexemeTypeString());  
            // 返会true告知还有下个词元  
            return true;  
        }  
        // 返会false告知词元输出完毕  
        return false;  
    }  
  
    /* 
     * (non-Javadoc) 
     *  
     * @see org.apache.lucene.analysis.Tokenizer#reset(java.io.Reader) 
     */  
    @Override  
    public void reset() throws IOException {  
        super.reset();  
        _IKImplement.reset(input);  
    }  
  
    @Override  
    public final void end() {  
        // set final offset  
        int finalOffset = correctOffset(this.endPosition);  
        offsetAtt.setOffset(finalOffset, finalOffset);  
    }  
}  